In many types of chemical and polymer processes, it is necessary to feed small quantities of a functional material to a reaction zone or to a molten polymer stream. Frequently considerable difficulties are encountered in introducing such functional materials at a continuous, uniform rate. These problems are especially difficult when it is necessary to feed finely-divided solid materials to a liquid or vapor medium, or where it is necessary to feed a material to a highly viscous liquid system such as a stream of molten polymer.
An example of a system in which a solid material must be added to a liquid reaction system sealed from the atmosphere is the introduction of finely-divided solid catalysts into olefin polymerizations that are carried out in a liquid hydrocarbon medium. A common method for introducing such catalyst solids to the liquid polymerization medium is to suspend the catalyst solids in a hydrocarbon medium, feed such a suspension to a cup maintained in a rotatable valve, and then to rotate the valve to dump the catalyst solids into the reaction medium. A typical catalyst feeding system of this type is shown in U.S. Pat. No. 3,257,363. By feeding the catalyst solids to the reaction medium in this manner, the catalyst is added to the reaction medium in finite charges on a discontinuous basis. As a consequence, in most instances, the concentration of catalyst particles varies in different sections of the polymerization medium.
In view of problems of the above types, it would be desirable to have available to the art improved compositions and methods for feeding functional materials to reaction systems on a truly continuous and uniform basis.